Mechanical wound closures by means of staples or clips are used in practically all surgical areas, in order to bind tissue and hold it together. For example, clips are used during anastomoses in the whole digestive tract, from the esophagus to the rectum, and also generally when setting sutures. The clips applied in such cases are made from bendable wire-like material and are bent into a closed form, which firmly encloses the tissue lying in between. Such clips and staple applying mechanisms are shown in the complete Ethicon, Inc., Somerville, N.J. catalogue published in 1989, pages 119 to 127.
The clips are placed in the staplers in a form which largely corresponds to that known from office staples. The lower part of FIG. 6 shows correspondingly formed conventional staples, which has a rectilinear bottom side or base 10; from the two ends 12 and 14 of which extend legs or limbs 42 and 44, projecting essentially at right angles. In use, the clip is bent into the closed staple shown in FIG. 6a with the use of a clip applier, and wraps round the tissue lying in between. The closed staple is essentially rectangular in shape, the limbs 42, 44 essentially forming the upper side of the rectangle and the base 10 becoming the bottom and the two sides of the rectangle.
Surgical staples are also used in modern minimally invasive operation techniques. In these operations, mostly called endoscopic or laparoscopic, the instruments needed for operative measures are introduced into the body through one or more trocar cannulae to the operation area, for example into the abdominal cavity, and controlled there under endoscopic monitoring. The trocar cannulae have a small diameter, in order that only minimal wounds occur when the trocar cannula is introduced through the abdominal wall; two sizes often used by surgeons allow passage of 5 mm and 10 mm instruments.
Staplers which are to be used endoscopically must likewise be introduced into the operation area through such trocar cannulae, the clips contained in the stapler lying with their bottom sides perpendicular to the longitudinal axis of the trocar cannula, and pushed forward in this position within the stapler. This produces the condition that the length of the base of the clip must always be less than the internal diameter of the trocar cannula. Since, for medical reasons, trocar diameters are usually pre-set for 5 mm and 10 mm trocars, the problem to date has been that only clips with a relatively small base length (and thus with a small perimeter and small overall size) can be used in endoscopic operations through trocar cannulae. An example of such appliers are those found in U.S. Pat. No. 5,174,487 and Ser. No. 07/759,014 (docket No. SEN-83), now U.S. Pat. No. 5,246,156, herein incorporated by reference.
FIG. 6 shows a conventional clip prior to setting. It has a straight bottom side or base 10 from whose ends 12 and 14 legs 42 and 44 project respectively. It is easy to see that much of the perimeter of the finally formed, essentially rectangular clip in the upper part of FIG. 6 comes from the originally straight base 10. The height (h) and width (b) of the closed rectangular clip (as in FIG. 6a) are approximately linked to the length of the base 10 prior to setting (L.sub.base) through the relationship b+2 h=L.sub.base, if one assumes that the base side (b) and the two lateral sides (1) of the set clip are formed from the base 10. A clip which has, for example, a width b=8 mm and a height h=6 mm after setting would, if formed conventionally, have a base length of some 20 mm. The clip to be introduced with its base transversely through a trocar cannula would thus require a trocar cannula with an internal diameter of more than 20 mm. Trocars of this size are not generally desirable as, when they are applied, the advantages of minimally invasive surgery would be somewhat compromised.
From German Patent No. 32 04 532 a surgical clip made from bendable wire-like material is known, in which before setting, the base does not run along a straight line but is bent backwards, opposite to the fully closed direction of the legs. In this way, the free ends of the legs and the vertex of the base lie approximately along one line. Because of this shape before setting, the staple is somewhat more compact than the clips described above, which have a straight base. The extension of the staple in DE 32 04 532 measured transversely with respect to the legs is, however, again significantly greater than the extension measured in the direction of the legs, so that introducing such staple also would require a large trocar cannula.